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The Unsinkable Water Strider

The Unsinkable Water Strider

Summer is fast approaching and soon they will be zipping at great rates of speed across the water.  No, I am not thinking of motor boats.    I am thinking of a creature that seemingly walks on water.  Better than that, they glide, like skaters, on a calm surface with confidence and determination, at speeds above three feet per second.  Water striders, otherwise known as pond skaters or even Jesus bugs, number about 1,700 species world-wide.  They are common insects in the watershed representing the ‘true bug’ division, the Hemipterans, whose defining characteristic is a beak-like mouth with piercing and sucking mouthparts, but truly the unique feature of water striders is their way of motorvating on water.  How do they do that? The answer has a few parts.   The first concerns the physical nature of water.  Water has a characteristic surface tension that relates to the positive and negative charges on each water molecule and they way they attract each other.  This leads to some of water’s properties, such as the way raindrops bead up on leaves and even why water can just drip from a leaky faucet.  For the water strider, the surface of water is elastic, and the insect can scoot around only causing slight dimples where its legs touch the surface.  This would not be possible without the cohesiveness of the water molecules on the surface.   But the insect also has two amazing adaptations for its life on the water.   One involves its set of legs.   The water strider has six legs but each pair is shaped differently and has different functions.   The short front pair are involved only with catching prey.   In the middle are the ‘oars’, two long thin legs that provide the propulsion for the insect’s movement, sweeping backward along the surface.   The hind legs are the longest and not only help steer and brake but along with the second pair aid in distributing the weight of the insect so it can best use the surface tension of the water and stay afloat.  The second feature is invisible to our eyes but as seen with a microscope, thousands of tiny hairs cover every part of the water strider’s body.  These so-called hydrofuge hair piles, their technical term, are waterproof, trapping tiny air bubbles in a groove along their length.   The insect is thus totally protected from being splashed and sunk by a wave.  However, they can go underwater under their own power to escape from a would-be predator.  They just then bob up to the surface again, totally dry.  Thanks to Wikipedia, National Geographic, and https://blog.  nature.  org/science/2017/04/10/7-cool-factswater-stridersskippers-pond-skaters-weird-nature/, Kaufman’s Field Guide to Insects of North America, and Steven Marshall’s Insects: Their Natural History and Diversity, Photo by cory